PURPOSE: To evaluate the clinical and radiologic findings of coronary artery fistula (CAF) by reviwing adult patients in whom this condition had been diagnosed by coronary angiogram. MATERIALS AND METHODS: We retrospectively analysed the clinical findings, chest X-rays and angiographic findings of 37 adult CAF patients treated at three institutes over a period of is 15 years. RESULTS: On coronary angiogram, the origin of CAF was found to be the left coronary artery (LCA) in 20 cases (54%), the right coronary artery (RCA) in five (14%), and both in 12 (32%). By subdividing the coronary artery into four segments [RCA, left main coronary artery, left anterior descending artery(LAD), and left circumflex artery(LCX)], the origin of CAF (total 55 cases) was found to be the LAD in 23 cases (42%), the LCX in 12 (22%), the left main coronary artery in three (5%), and the RCA in 17 (31%). The draining site of CAF was the right heart [right atrium, right ventricle, and main pulmonary artery (MPA)] in 28 cases (75%) the left heart (left atrium and left ventricle) in 8 (22%), and both in one (3%). The fistula drained to the cardiac chamber in 12 cases (33%), the MPA in 23 (62%), and both in 2 (5%). Among 55 cases, the total number of fistulas to the MPA was 35, and their origin was the RCA in nine instances (26%), and the left coronary artery in26 (74%). CAF to the MPA was classified into four types : Type I (single, tortuous and not dilated) was seen in six patients (17%), type II (single, tortuous and dilated) in three (9%), type III (multiple and fine plexus) in 21 (60%), and type IV (multiple and dilated plexus) in five (14%). Eighteen cases (49%) were associated with the other cardiac disease. CONCLUSION: In these Korean adults, CAF originated most commonly from the LCA, especially from the LAD segment of this artery, and most frequently drained to the right cardic chamber, especially to the MPA. The morphology of the CAF to the MPA was mostly multiple and fine plexus. We suggest that to ensure the most suitable treatment, and for better prognosis, patients with other cardiac disease should be evaluated for the presence of CAF.